The manufacture of cellulosic insulation in accordance with the present state of the art begins with a grinding operation in which newspapers are shredded to provide a mass of cellulosic fibers.
A fire retardant composition is then mixed with the cellulosic fibers in order to coat them with the fire retardant material. This mixing is conventionally accomplished in one of two manners.
The fire retardant may be dissolved in a suitable solvent such as water and then sprayed into a stirred mass of the shredded cellulosic material. The spray application of the retardant may be performed simultaneously with a grinding step for shredding the cellulosic material or as a subsequent step.
One of the major disadvantages of the solution spray application system is that the resultant mixture becomes a sticky, gummy mess which is difficult to handle and requires drying.
Alternatively fire retardant may be applied in dry, powdered form which may be mixed with stirred cellulosic fibers during a grinding operation or an independent stirring operation. However, difficulty is experienced in effecting the adhesion of the fire retardant particles to the cellulosic shredded material with a sufficiently durable bond. It also has been difficult or impossible to obtain a complete and uniform coating of fire retardant on the cellulosic particles.
These latter problems have, in the current state of the art, been reduced somewhat by spraying small quantities of water on the cellulosic material before mixing in the fire retardant in order that the dry fire retardant particles will be wetted when they come into random contact with the cellulosic fibers. Thus, the cellulosic fibers are adhered to the cellulosic fibers by the wetting activity of the moisture.
However, even this system has several disadvantages including the still somewhat agglomerated or clumpy nature of the finished product, the non-uniform and incomplete coating of the fibers and the need for drying the insulation after the retardant is applied.